Various abiotic stresses lead to the production of reactive oxygen species (ROS) in plants which may cause severe damage in cell organales. Therefor I would like to know the actual definition of ROS and also its functional activities in plant cell.
You can refer following paper..
http://www.sciencedirect.com/science/article/pii/S0981942810001798
ROS are formed from molecular oxygen through one-electron reduction series, O2, O2–, H2O2, OH, H2O. Molecular oxyegn is table but possibly highly reactive because of this. ROS can be extremely damaging to biological macromolecules. Oxygen itself is a waste product of first photosynthetic cyanobacteria, and since that time other organisms evolved ways to cope with a potential toxicity of oxygen through developing of enzymatic antioxidative systems. More stable ROS, like H2O2, have also cellular signaling function leading to changes in gene expression.
In addition, ROS are produced all the time, even during the "normal" metabolism. Photosynthesis is the main source of ROS.
Indeed, ROS are generated as by-products of the most essential energy-generating processes, photosynthesis and respiration. Together with an extensive battery of oxidases, chloroplasts, peroxisomes, and mitochondria are the main organellar ROS producers (Vranová et al., 2002; Apel and Hirt, 2004). Despite an efficient antioxidant machinery in these organelles, subtle changes in ROS homeostasis are inevitable (Foyer and Noctor, 2005). When the increase in ROS is relatively small, the housekeeping antioxidant capacity is sufficient to reset the original balance between ROS production and scavenging, thus reestablishing redox homeostasis. Under growth-limiting environmental conditions, this delicate redox balance is easily disturbed, potentially leading to a significant ROS accumulation. In fact, a 3- to 10-fold increase in ROS levels has been calculated under stress conditions (Polle, 2001). Thus, it is not surprising that a transient oxidative burst and a subsequent temporary shift in the intracellular redox state are common features of both biotic and abiotic stress responses (Dat et al., 2000;Mittler et al., 2004). Under unfavorable environmental conditions, such as temperature extremes, drought, or salt stress, the rate of carbon fixation is limited, causing an increase in photoinhibition potentially steering the photosystem toward overproduction of superoxide radicals and H2O2 (Foyer and Noctor, 2005). Similarly during ozone exposure, ROS are generated following the entry of ozone through the stomata and its conversion in the leaf apoplast, eventually leading to the formation of HR-like lesions (Pellinen et al., 1999;Rao and Davis, 2001).
Dear All,
Kaumeel Chokshi, Gederts Ievinsh and Heshmat Soliman Aldesuquy . Greetings. I am really happy to find this by answering all of you. I hope further if I have any problem regarding any research you will help me.
Best Regards
Reactive oxygen species are oxygen-derived molecules that act as powerful oxidants and may form via a large number of physiologic and non-physiologic processes. Although these molecules play a role in the oxygen-dependent defence mechanism of polymorphonuclear leukocytes against bacteria, they may also be highly damaging, as they can attack biologic macromolecules, including lipids, proteins, and DNA, and lead to significant tissue damage. Molecular oxygen is relatively not reactive but oxygen derivatives more prone to participate in chemical reactions (reactive oxygen species; ROS) are formed during aerobic metabolism and in the environment. The omnipresence of ROS has forced aerobes to mount complex antioxidant defence which still appears to be inadequate in ROS-mediated aging and in number of diseases.
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